It is well recognized that, for certain medications, the most effective means of administration is in the form of a mist or plume inhaled by the user. In connection with the treatment of asthma, for example, such inhalation provides the most direct and effectual path to the lungs for bronchial dilation therapy, having substantial benefits over ingested or intravenous treatments. The inspiration of, for example, an epinephrine spray typically provides prompt and immediate relief.
There are a variety of mechanisms for use in conjunction with metered dose inhalation (MDI) dispensers, typically for asthma treatment, which are intended to permit the medication to be transported to the user's lungs during the inspiratory breath. In U.S. Pat. No. 5,040,527 of the present inventors and assigned to the assignee of record herein, a measured dose of medication from an MDI dispenser is directed against the flow of inspiratory air developed by the user. The medication release is timed to coincide with a rapid increase in such inspiratory flow. The resulting flow of inspiratory air contacting the oppositely-directed medication provides for mixing of the flows and the carrying of the medication deep into the lungs of the user.
The present invention is based upon the recognition by the inventors that the introduction of a counter-directed medication flow into a primary flow intended for inspiration can be used to improve the blending and dispensation of medication in a variety of situations, beyond that where the driving force for the inspiratory flow is developed solely by the breathing action of the patient.